In the latest study, researchers compared exposures to a variety of pesticides, as recalled by the mother, among children with leukemia and those without the disease.

They concluded that the risk of developing acute leukemia was almost twice as high in children whose mothers reported using insecticides in the home while pregnant and when their children were small.

Use of insecticidal shampoos to treat head lice and exposure to garden insecticides also appeared to roughly double a child's risk of developing leukemia.

Head Lice Link Preliminary

Epidemiologist Florence Menegaux, MD, PhD, led the research team. She says the head lice shampoo findings, especially, should be interpreted with caution because hers is the first study to link insecticidal shampoos to childhood leukemia.

American Cancer Society (ACS) spokesman Len Lichtenfeld, MD, agrees that the study's findings must be replicated before any conclusions can be made.

"We do not believe that there is anything in this study that should deter parents from treating their children with these shampoos," he tells WebMD.

Previous, similarly designed studies have suggested a link between prenatal and postnatal indoor pesticide exposure and childhood leukemia, however.

"People need to be aware that while it is not conclusive, the evidence that this is a potential risk is certainly there," Menegaux says. "Six studies before this one came to the same conclusion."

'Intriguing' Evidence

Menegaux's study included 280 children with newly diagnosed leukemia and 288 children without the disease.

Interviews were conducted with the mothers of all of the children. The mothers were asked about both parents' work history, the use of insecticides in the home and garden, and the use of head lice shampoos.

The findings are published in the latest issue of the journal Occupational and Environmental Medicine.